With the increase in the volumes of digital contents, wireless connection means of more than 1 Gbps is desired in information devices. As high-speed wireless connection means, millimeter-wave wireless communication using the 60-GHz band is promising. In recent years, transistor characteristics have improved because the process has been made fine, and operations in the 60-GHz band are also possible in CMOS devices.
A problem with the millimeter-wave wireless communication is that the higher the ability for the radio waves to advance straight is, the easier communication is intercepted by an intercepting object. One of the methods for solving the problem is beam forming.
Beam forming is a technology of arbitrarily switching the directivity of an array antenna by controlling the phase of the radio signal of each antenna at a plurality of antennas constituting the array antenna. By controlling the phase of the radio signal of each individual antenna so that the radio field intensity is an intense emission angle by using beam forming, efficient communication become possible. Moreover, in addition to wireless communication, in the field of radar, the beam forming technology is also used for accurately detecting the object.
Here, an important component circuit for implementing beam forming is a phase shifter. In order to make phases of 0 to 360 degrees variable, the phase shifter has, for example, a variable phase shifter that changes phases of 0 to 180 degrees and a polarity-switching amplifier circuit that switches a phase of 0 degrees or 180 degrees. Examples of conventional polarity-switching amplifier circuits include the one described in Non-Patent Document 1.